latest images brought many video playback and codec fixes. please update to the very latest and try again. i had this similar issue with firefox playing videos in android, which works after the update
I also figured someone might be interested in knowing that Amazon Prime Video android app works in the android container with a caveat:
If you have FuriOS autorotate the screen (or you manually rotate the screen), the rotation will be messed up. If you fix FuriOS to portrait, start a video, then press Amazon Prime Video’s fullscreen button, the video will play in landscape as expected.